Computer networks and the devices and services that reside on them are often the subject of attacks by parties that are attempting to improperly access information and resources or to introduce malicious code to the networks. One type of attack is based on a NOP slide or sled, wherein a sequence of no-operation (NOP) or NOP-like instructions causes the CPU's execution to flow from a point of entry into the sequence towards a branch instruction that contains an address for the attack function code. A NOP sled typically contains a long series, e.g. “landing pad”, of NOP or NOP-like instructions to increase the likelihood of execution branching into the NOP sled and initiate execution that leads to the branch instruction, which branches to a malicious code payload.
One property of NOP sleds, that of being executable from any or most starting offsets and having the same effect regardless of which starting offset is used, we consider to have the property we term omnientrancy, or to be omnientrant.